Dental device and method of making dental crowns



L. L. COHEN Oct. 16, 1962 DENTAL DEVICE AND METHOD OF MAKlNG DENTAL CROWNS Filed March 18, 1960 FIG. 3

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FIG.6

FIG.9

INVENTOR. I 50 1. COHEN v BY %Q A 3,058,216 DENTAL DEVIQE AND METHOD OF MAKING DENTAL CROWNS Leon L. Cohen, 40 Schenck Ave., Box 494, Great Neck, N.Y. Filed Mar. 18, 1960, Ser. No. 16,030 4 Claims. (Cl. 3212) This invention relates to a dental device and method useful by dentists or dental technicians to fabricate a por celain veneer crown of permanent and lasting fit, thereby greatly simplifying and reducing the cost of otherwise difficult and expensive dental techniques.

Plastic jacket crowns and plastic veneer crowns ever since their introduction to and use by the dental profession have met with disfavor because of inherent faults due to instability of color and fit of the materials employed. The more stable materials, such as the all porcelain jacket crown and various types of porcelain veneer crowns, are expensive and difiicult to construct in large part because of the excessive time and cost of labor involved The present invention is predicated upon the provision of prefabricated molds of various shapes, sizes and colors, hereindter termed a porcelain veneer plastic crown, which can be rapidly and rather inexpensively employed in lieu of the previous materials and practices By means of the present invention, a porcelain veneer crown can be produced with accurate and permanent fit and with a highly esthetic appearance at a fraction of the time and cost according to prior practices The porcelain veneer plastic crown provides a wide range of prefabricated tooth forms with a porcelain veneer facing attached so as to meet all the requirements of dentists and dental technicians In the accompanying drawing,

FIG. 1 is a face View of a convex or glazed porcelain veneer facing;

FIG. 2 is a view of the reverse side of FIG. 1 showing surface irregularities for a purpose to be mentioned hereinafter;

FIG. 3 is a perspective view below the eye of the observer of the porcelain veneer plastic crown form or mold;

FIG. 4 shows the form or mold of FIG. 3 applied to the stump of an upper tooth and showing the relative location of the gum line, the form or mold having been filled with a suitable investment material;

FIG. 5 shows the form or mold removed from the tooth and the manner of grinding away excess material;

FIG. 6 is similar to FIG. 4 but wherein the product of FIG. 5 is applied to the tooth stump;

FIGS. 7 to 9 show steps in conventional casting procedure but using the product of FIG. 5;

FIG. 10 shows the casting by itself as produced in the step of FIG. 9;

FIG. 11 is the same as FIG. 10 but with the cast shank removed, and

FIG. 12 shows the completed device in place on a tooth stump.

The porcelain veneer plastic crown form of FIG. 3 is composed of the convex porcelain facing 10 assembled with and secured to a complementary plastic portion 11 which completes the form or mold, the irregular surface of the concave side of the facing 10 being designated as 12. The plastic material 11 is composed of any suitable or known synthetic plastic, such as polystyrene or acrylic (methyl methacrylate) resins or any other available plastic material and is preferably clear or translucent. The porcelain facings are glazed, shaped and shaded in the factory to simulate the face of natural teeth and the roughened or uneven reverse surface of the facing makes it possible to cast a precious or non-precious metal thereto with a firm and strong bond. It is pointed out that the facings and the plastic complements are mass produced inexpensively in a wide range of sizes, shapes and colors so as to have adequate versatility to meet the needs of dentists and dental technicians.

The porcelain facings and plastic complements are secured or attached in the relationship shown in FIG. 3 by hand or machine and the assembly resembles a jacket crown or tooth form with a front of porcelain and a back of plastic. This form or mold is then fitted over the stump or core 13 of tooth 14 up to the gum line 15 and suitable impression material 16 introduced into the form or mold. It will be observed from FIG. 4 that the form or mold is oversize and hence after it is fitted over the tooth stump or core 13 and an impression made in the impression material 16, it is removed and ground down as shown in FIG. 5 by a conventional grinding stone '17 rotated at high speed in the usual manner through the stem 18. The resulting product at this stage is then refitted over the tooth stump or core and at such stage has the construction and appearance shown in FIG. 6-.

It is understood also that after the form or mold is removed from the tooth stump or core in FIG. 4-, a model can be made from the impression of the stump in the im-.

pression material. It is further understood that when using the grinding stone, the porcelain portion of the form or mold is carefully adapted to the face of the stump or core so that its position in the arch of the mouth is pleasing and in harmony with the remaining teeth. The plastic portion of the form or mold is oversize and is trimmed or adjusted so that it is just long enough to cover the stump or core or very slightly longer. At such stage the form or mold is fitted over the stump or core to provide a preformed and preshaded porcelain crown with a cavity into which the tooth stump or core fits. The material 16 is a powdered form of a similar type of plastic generally known in dentistry as a quick-curing acrylic or impression material and this is pressed against the tooth stump or core while the impression material is still in a moldable state. The crown at this point is pleasing and harmonious in appearance and makes an accurate fit to the tooth stump or core and upon grinding away of the excess material as in FIG. 5, the fit is then such that it is in complete harmony with adjacent teeth and with the bite of opposing teeth. In this manner the fit is like a natural crown of enamel at the gum line. As is familiar to dentists, the form or mold in this state can be applied to the tooth stump or core as many times as is necessary with intervening grindings so as to get a perfect fit.

When this is accomplished as is shown in FIG. 6, the form or mold is removed and is provided with a sprue 19 having an inverted funnel-shaped lower extremity 20 and is invested in known manner in a casting ring 21 similar to that used in making any type of dental casting or other small metal casting and containing the investment material 22. This investment material hardens and the sprue 19 is then removed, and the form or mold with the surrounding impression material turned out of the casting ring leaving the porcelain veneer facing in place. Heat is applied through the passage 23 remaining after the removal of the sprue and the space left by the burning away of the remainder of the crown and impression material is filled with molten metal as shown in FIG. 9 which is introduced in any known or suitable manner, i.e., centrifugally or by pressure or vacuum to force the molten metal to fill the empty space. The molten metal bonds itself to the serrated inner surface 12 of the porcelain facing 10 and assumes the shape of the adjusted plastic veneer crown.

Upon cooling the porcelain veneer crown which has been formed within the mold, it can be removed and with a minimum amount of time and effort can be fitted and adjusted to the tooth stump or core just as accurately as the porcelain veneer plastic crown was fitted as above described. The shank-like portion 25 (see FIGS. 9 and 10) of the casting is removed thereby providing the porcelain-metal crown form of FIG. 11 which after the usual or necessary adjustments in-fit is applied to the tooth stump or core as shown in FIG. 12 which represents the final objective of the invention. This porcelain veneer crown is set or attached to the tooth stump or core by. a dental cement or binding material.

In this way a porcelain veneer crown can be made rapidly and inexpensively and Without any elaborate or difiicult technique. In this way also the desirability of this type of crown canv be made widely available in contrast to the fact that such has heretofore only been available to those able to afford the very considerable expense involved.

The porcelain veneer plastic form or mold of FIG. 3 can further be employed for replacement by the same technique except that in such case instead of making a fit to a tooth stump or core, it is much simpler to make the fit to the model which was made as above mentioned. In this way missing teeth can be replaced by adding impression material to the mold or form and pressing it firmly into the space left by a missing tooth and then carrying out the necessary fit adjustment and casting in the manner already described.

As far as I am aware, the device and procedure hereinabove described and hereinafter claimed represent a basically new approach and provide a simple inexpensive way of carrying out what is presently a laborious, painstaking and expensive type of dental service.

What is claimed is:

1. A dental form for use in the production of dental crowns comprising a porcelain facing having a smooth convex front surface and a roughened concave back surface and a smooth-surfaced synthetic plastic rear portion of concave-convex section, the porcelain facing and the plastic rear portion being secured together to form a mold cavity therebetween.

2. A dental form for use in the production of dental crowns comprising a porcelain facing having a smooth convex front surface and a roughened concave back surface and a smooth-surfaced synthetic plastic rear portion of concavo-convex section, the porcelain facing and the plastic rear portion being secured together to form a mold cavity therebetweeu, said mold cavity containing dental impression material moldable over a tooth stump.

3. A dental form for use in the production of dental crowns comprising a porcelain facing having a smooth convex front surface and a roughened concave back surface and a smooth-surfaced synthetic plastic rear portion of concave-convex section, the porcelain facing and the plastic rear portion being secured together to form a mold cavity therebetween, said mold cavity containing dental impression material moldable over a tooth stump and said plastic portion and impression material being removable by burning and replaced with metal afiixed to the roughened concave back surface of the porcelain facing.

4. In a method of making a porcelain-metal dental crown which comprises securing a porcelain facing with a roughened back surface to a smooth-surfaced synthetic plastic part to form a mold, introducing moldable impression material into the mold, applying the assembly to a tooth stump to make a corresponding impression in the impression material, fitting and adjusting the same to the patients mouth and gum line, burning out the plastic and impression material and replacing the same with metal secured to the roughened back surface of the porcelain facing.

OTHER REFERENCES Metal Melt Advertisement, page 1, received in Div. 55, November 28, 1947. 

